The present invention relates generally to gas turbine engines, and more particularly to radial and axial retention and spacing in gas turbine engines.
Gas turbine engines comprise at least one spool comprising a compressor and a turbine on a shared shaft. Many modern gas turbine engines comprise two, three, or more spools on concentric shafts configured to rotate at different speeds. Both compressors and turbines comprise one or more stages of alternating stationary vanes and rotating blades. The rotation of compressor blades relative to stationary vanes compresses inlet air. The resulting high-pressure gas is mixed with fuel and ignited at a combustor. The resulting high-temperature, high-pressure airflow rotates turbine rotors, which in turn drive the compressor via the shared shaft.
Gas turbine engines exist in a variety of configurations. Turbojet engines operate substantially as described above. Turboshaft engines drive rotary loads such as propeller blades via a power turbine, typically situated on a separate spool. Turbofan engines are high-bypass systems with large-diameter inlet fans on a low-pressure shaft typically shared with a low pressure compressor and a low-pressure turbine. Turbojet, turbofan, and turboshaft engines may all comprise multiple spools (e.g. a two-spool system with high and low pressure shafts, turbines, and compressors, or a three-spool system with high, intermediate, and low pressure shafts, turbines, and compressors).
Gas turbine engine components are assembled as an axial stack including both stationary and rotating components. These components are constructed with tolerances to allow for variations arising from part manufacture and assembly. Axial tolerances may be taken in by positioning adjacent axial components with spacers machined to locate rotatinghardware at an optimum location relative to static structure. Positioning spacers are commonly situated between rotating shafts and bearing assemblies of adjacent supporting stationary structures.
Axial loads in gas turbine engines are commonly secured in tension by means of threaded nuts and tie bolts or shafts that cap a portion of an axial stack. To prevent nuts from tightening or loosening, some gas turbine engines use lock washers with crenellations or other antirotating-structures. Tie shaft nuts and lock washers contribute weight, stack length, and cost to the gas turbine engine. A lightweight, highly axially compact gas turbine engine is desirable for many vehicular applications.